Assistant
Definition
By: Gregory R. Waryasz, MD
The elbow joint of the musculoskeletal system is characterized by connecting the arm and the forearm.
It is part of the upper extremity and consists of bone, skeletal muscle, cartilage, synovial tissue, and tendon.
Its unique structural is that it is a hinge type of synovial joint. There are humeroulnar and humeroradial articulations. Some consider the elbow to be a trochnoginglymoid joint with three articulations including the humeroulnar, radiohumeral, and the proximal radioulnar joint. The addition of the proximal radioulnar and the radiohumeral joints add in the rotation component of the forearm.
The bones are the humerus’s trochlea and capitellum, radial head, and the trochlear notch of the ulna. The articular surfaces are covered with hyaline cartilage.
The ligaments are the radial collateral, annular ligament of the radius, and the ulnar collateral ligament.
The bursae include the intratendinous olecranon bursa, subtendinous olecranon bursa, subcutaneous olecranon bursa, and the bicipitoradial bursa. Less clinically relevant bursae include the bursa of the anconeus, bursa at the origin of the extensor carpi radialis brevis, subcutaneous bursa of the medial epicondyle, and the subcutaneous bursa of the lateral epicondyle.
The blood supply is from the anastomosis around the elbow joint.
The innervation is from the musculocutaneous, radial, and ulnar nerves.
The elbow joint’s components as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in the embryo.
The function of the elbow joint is to flex and extend the upper extremity at the junction of the arm and forearm. Full extension produces a 170 degree angle between the humerus and ulna. This is known as the carrying angle.
The elbow flexors are the brachialis and biceps brachii. The brachioradialis performs rapid flexion when there is no resistance. With resistance, the brachioradialis and pronator teres help to assist with slower flexion.
The elbow extensors include the triceps brachii and weakly by the anconeus.
Some anatomists and surgeons also include the radiohumeral and proximal radioulnar joint into the elbow joint. These allow for pronation and supination of the forearm.
Supination occurs by the supinator and the biceps brachii. There is some supination from the extensor pollicis longus and the extensor carpi radialis longus.
Pronation occurs from the pronator quadrates and the pronator teres. Other muscles that assist with pronation include the flexor carpi radialis, palmaris longus, and brachioradialis.
Common diseases of the elbow joint include fracture, dislocation, bursitis, tendinitis, arthritis, septic arthritis, transient synovitis, osteochondritis dissecans, Panner disease, Hegemann’s disease, stress fracture, and ligament injury.
Fractures can occur in the humeral, radial, or ulnar components of the elbow joint. There can be an associated dislocation with the fracture.
Dislocation without fracture can also occur.
Osteoarthritis is a condition of joint space narrowing leading to pain. Rheumatoid arthritis is a condition of an autoimmune reaction against the synovial tissue.
Tendinitis is a condition of overuse resulting in inflammation of the tendon. The medial or lateral epicondyle can be the site of tenderness. Medial epicondylitis is a condition of pain and tenderness in the medial elbow at the site of the common flexor tendon origin. It may begin as a microtear between the pronator teres and the flexor carpi radialis. It may be associated with ulnar neuritis. Lateral epicondylitis or Tennis elbow is most commonly due to the extensor carpi radialis brevis tendon origin. It is a common orthopaedic condition that occurs in patients who are recreational athletes or those that engage in repetitive daily activities. Patients do not have to play tennis to have the condition.
Bursitis can occur at any of the bursa due to overuse/friction leading to inflammation of the bursa. It can also be due to infection.
Ligament injuries can occur including full thickness or partial tears.
Nursemaid’s elbow is a condition of subluxation of the radial head associated from axial traction. This can occur when parents hold their children in the air by the hands or forearm.
Transient synovitis or toxic synovitis is joint pain after a recent viral illness or trauma. It is a self-limiting condition of patients ages 3 to 8 years.
Lyme Arthritis is a condition common in the northeast USA where there is a rheumatologic reaction to Borrelia burgdoferi. It occurs after the patient is bitten by a tick.
Osteomyelitis is an infection of the bone typically caused by a bacteria.
Osteoporosis is a condition of low bone mineral density that can predispose an individual to fractures.
Septic arthritis is an infection of the synovial tissue of the joint with pus in the joint cavity. The infection is capable of rapidly destroying the joint.
Osteochondritis dissecans is an osteochondral defect with partial or complete separation of a bone fragment.
Panner disease is an osteochondrosis of the capitellum seen in younger patients.
Hegemann’s disease is a condition of osteonecrosis of the humeral trochlea.
A stress fracture of the medial epicondyle can occur in children specifically baseball pitchers.
Commonly used diagnostic procedures include clinical history, physical exam, x-ray, CT, and MRI.
It is usually treated with rest, NSAIDs, physical therapy, and possibly surgery. Dislocation/subluxation and fractures may not respond to nonoperative treatments and may require surgery. Arthritis can be treated with NSAIDs and physical therapy, but may require surgery including joint replacement. Tendinitis and bursitis are treated with rest, NSAIDs, physical therapy, and corticosteroid injections. Septic arthritis requires surgical washout and antibiotics. Transient synovitis is treated with NSAIDs. Ligament tears may require surgical reconstruction. Panner disease and Hegemann’s disease are treated nonoperatively with rest, physical therapy, and NSAIDs.
References
Davis MF, Davis PF, Ross DS. Expert Guide to Sports Medicine. ACP Series, 2005.
Elstrom J, Virkus W, Pankovich (eds), Handbook of Fractures (3rd edition), McGraw Hill, New York, NY, 2006.
Koval K, Zuckerman J (eds), Handbook of Fractures (3rd edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.
Lieberman J (ed), AAOS Comprehensive Orthopaedic Review, American Academy of Orthopaedic Surgeons, 2008.
Moore K, Dalley A (eds), Clinically Oriented Anatomy (5th edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.
Wheeless’ Textbook of Orthopaedics: Elbow Joint Menu (http://www.wheelessonline.com/ortho/elbow_joint_menu)